import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        Media[] ms  = new Media[n];
        for (int i=0; i<n; i++) {
            String type = sc.next();
            if (type.equals("book")) {
                ms[i] = new Book(sc.next(), sc.nextDouble());
            }else {
                ms[i] = new DVD(sc.next());
            }
        }
        double rent = MediaShop.calculateRent(ms, sc.nextInt());
        System.out.printf("%.2f", rent);
    }
}

/* 请在这里填写答案 */

/* 请在这里填写答案 */
class Book extends Media{
    String name;
    double price;

    public Book(String name, double price) {
        this.name = name;
        this.price = price;
    }

    public double getDailyRent() {
        return 0.01*price;
    }
}
class DVD extends Media{
    String name;

    public DVD(String name) {
        this.name = name;
    }

    @Override
    public double getDailyRent() {
        return 1;
    }
}
class Media{
    public double getDailyRent(){
        return 0;
    }
}
class MediaShop{
    static double calculateRent(Media[] medias, int days){
        double sum = 0;
        for (Media t : medias){
            if (t instanceof Book){
                sum += t.getDailyRent()*days;
            } else if (t instanceof DVD) {
                sum += t.getDailyRent()*days;
            }
        }
        return sum;
    }
}